Ammonolytic Hydrogenation of Secondary Amides: An Efficient Method for the Recycling of Long-Chain Polyamides

Long-chain polyamides (LCPAs) are depolymerized by ammonolysis of the secondary amide bonds into building blocks for new polymer synthesis. Research on PA is quite limited and often proposes harsh reaction conditions with homogeneous catalysts. Here, we describe a heterogeneous catalytic system based Nb2O5. Reactions were performed at relatively low temperature 200 °C in cyclopentyl methyl ether (CPME) as green solvent addition NH3 H2. The amides was extensively studied, initially N-hexylhexanamide model compound. Since an equilibrium reaction, it eventually coupled to hydrogenation process, RuWOx/MgAl2O4 catalyst, order achieve complete depolymerization. Industrial LCPA samples successfully completely ?,?-diamine monomers oligomers, resulting product distributions 62% primary amines 36% amines. proven be very robust against variety contaminants, e.g., fillers, other plastics, additives. Only sulfur-containing compounds poison Ru-catalyst have removed completely.